It looks like meson is picking compiler flags from pkg-config and consequently setting include paths to dependencies using the -I flag. This leads to annoying warnings if you start turning on enough warnings.

Is there a way to work around this. I was thinking if gcc had some flag to consider header files under /usr to be system header anyway, but I didn’t find such flag. Or if there’s a meson-trick to make it use -isystem instead to point out the include path to (some) dependencies.